Hydrogeological Survey Methods

𝗦𝗧𝗔𝗕𝗟𝗘 𝗜𝗦𝗢𝗧𝗢𝗣𝗘𝗦 𝗜𝗡 𝗛𝗬𝗗𝗥𝗢𝗟𝗢𝗚𝗬 Understanding where our groundwater comes from and how it replenishes is critical for sustainable water management. But how do we trace a resource hidden deep underground? The answer lies in the water molecules themselves. By analyzing the 𝘀𝘁𝗮𝗯𝗹𝗲 𝗶𝘀𝗼𝘁𝗼𝗽𝗲𝘀 𝗼𝗳 𝗼𝘅𝘆𝗴𝗲𝗻 𝗮𝗻𝗱 𝗵𝘆𝗱𝗿𝗼𝗴𝗲𝗻 (𝗢𝘅𝘆𝗴𝗲𝗻-𝟭𝟴 𝗮𝗻𝗱 𝗗𝗲𝘂𝘁𝗲𝗿𝗶𝘂𝗺), we can effectively "𝗳𝗶𝗻𝗴𝗲𝗿𝗽𝗿𝗶𝗻𝘁" water sources. Here is how isotope hydrology is transforming groundwater analysis: 𝗧𝗿𝗮𝗰𝗶𝗻𝗴 𝘁𝗵𝗲 𝗢𝗿𝗶𝗴𝗶𝗻: Precipitation, soil water, and surface water all have distinct isotopic signatures based on climate, altitude, and seasonal effects. 𝗧𝗿𝗮𝗰𝗸𝗶𝗻𝗴 𝗘𝘃𝗮𝗽𝗼𝗿𝗮𝘁𝗶𝗼𝗻: Lighter isotopes evaporate more easily. When surface water is exposed to the sun before recharging an aquifer, it leaves behind an "enriched" signature of heavier isotopes that we can detect. 𝗣𝗹𝗼𝘁𝘁𝗶𝗻𝗴 𝘁𝗵𝗲 𝗙𝗹𝗼𝘄: By comparing groundwater samples against the Global Meteoric Water Line (GMWL), we can clearly map out direct recharge (rapid infiltration from rain) versus indirect recharge (infiltration from rivers or lakes). 𝗤𝘂𝗮𝗻𝘁𝗶𝗳𝘆𝗶𝗻𝗴 𝗠𝗶𝘅𝘁𝘂𝗿𝗲𝘀: Isotope data allows us to build mass balance models, helping us quantify the exact contributions of multiple water sources, including identifying ancient "paleowater." Whether we are estimating recharge rates, mapping aquifer connectivity, or tracing contamination, stable isotopes provide a powerful, natural tracing tool that does not rely on artificial dyes or chemicals. What isotopic methods have you found most effective in your field studies? Let me know in the comments! 👇 #Hydrogeology #WaterManagement #IsotopeHydrology #Groundwater #Sustainability #EnvironmentalScience #WaterResources

✨ Self Potential (SP) Method 🗣️SP is a passive electrophysical method that relies on measuring the spontaneous or natural electrical potential (natural electrical potentials (mV) in the ground without injecting current ) commonly associated with the weathering of sulfide ore bodies developed in the ground due to: Electrochemical reactions between minerals and subsurface fluids. Applications of the Self-Potential Method: 📌Exploring metallic deposits, especially sulfides. 📌Detecting the direction of groundwater flow. 📌Monitoring dams and reservoir integrity. 📌Detecting leaks in earth dams and reservoirs 💡How it Works: 1. Below the water table, pore fluids oxidize, releasing electrons. 2. Electrons flow upward through the conductive ore body. 3. At the top, reduction occurs-creating a stable negative "terminal." 4. Subsurface currents produce a characteristic negative anomaly at the surface. 🛠️Field Setup & Survey: Electrodes: Non-polarizable (e.g., Cu–CuSO₄ or Pb–PbCl₂). Array: Fixed reference electrode + moving electrode. Spacing: 5–20 m for detail, depending on target size. Corrections: Diurnal drift, cultural noise (pipelines, cables, etc.). 📊 Interpretation 📉Negative anomalies = often linked to ore body (oxidizing sulfides). 📈Positive anomalies = sometimes related to recharge zones or other electrochemical cells. Depth estimation is indirect; SP gives more of a qualitative anomaly map than exact depth 🔔In mineral exploration, anomalies come mainly from electrochemical potentials at the boundary between oxidized and unoxidized zones of sulfide bodies. When sulfides oxidize (pyrite, chalcopyrite, etc.), an electrochemical cell forms → electrons move inside the ore body, while ions move in groundwater. ✅ Bottom line: SP is a classic tool to detect oxidized caps (gossans) and buried sulfide zones, especially for VMS deposits. If you’re hunting gold associated with these systems, SP helps locate the sulfide host, but you’ll need Resistivity/IP follow-up for 3D mapping and chargeability (to confirm sulfides). 💡Gossan,VMS : In this systems, massive sulfides at depth create strong SP anomalies (–50 to –500 mV typical). Gold often occurs with or near sulfides in these systems, so SP anomalies can vector toward gold mineralization indirectly. 📌So SP helps: *map the top of sulfide zones beneath gossans, even if gold itself is not directly detectable. *Outline the oxidation zone thickness. *Indicate buried sulfide mineralization continuity. ✅Advantages : Low-Cost, fast, no current injection. Sensitive to sulfide oxidation → excellent for early reconnaissance. Works well in humid/wet environments where electrochemical cells are active. ✅Limitations Non-unique interpretation: anomalies could be cultural noise, groundwater flow, graphite, etc. Very sensitive to noise. Needs good referencing and noise control (cultural, telluric noise). Gold itself is not detectable — you’re tracking sulfide hosts, not the metal.

My first project with Halcrow in early 1972 was the GLC "London Roads in Tunnel Study which was associated with the collection and analysis of well & borehole information for the Greater London area enabling one to generate a simple computerized geological model (possibly the first) allowing fast assessment as to the geology & ground conditions associated with any future road or rail tunnel under London. The principal sources of geological and hydrogeological information were (1)  Borehole information from site investigation reports held by the British Geological Survey, the GLC & by various consultants. (2)  The maps and memoirs of the British Geological Survey particularly those related to water supply boreholes/well drilled in London including numerous early well records sunk towards the end of 18th century.  (3)  Well Records (Thames Water) .       Most of the information was held at the British Geological Surveys Offices located at Princes Gate, Kensington and at the time given that it was forbidden to have a photocopy of each well/borehole log including those held on microfilm, endless hours were spent going through and recording the relevant information from each log onto a proforma designed for the project. If photocopying had been allowed this would have provided additional valuable information to support the database. Thankfully now the BGS provide valuable information to all interested parties.   The information entered onto the proforma for each well/borehole .detailed the following : (i)     National Grid Easting and Northing coordinates (ii)   Ground level with respect to Ordnance Datum (iii) Depth below ground level to :  -   top of London Clay and thus depth/nature  of made ground and superficial deposits which if known were recorded -   top of Woolwich & Reading Beds including the recording as to the depth and nature of Upnor & Thanet Sands if known -    top of Upper Chalk -    water level within the Woolwich & Reading Beds and Thanet Sands -    water level within the Upper Chalk (iv) Reference to source, date and accuracy of the borehole or well information A total of 2500 borehole or wells were included in the database, mostly being deep located in the centre of Greater London with paucity of information in the outer suburbs especially on the Upper Chalk outcrop. Processing of the data included the removal of duplicate wells & boreholes obtained from the various sources. Outputs from the database using the SACM computer package included geological sections, three dimensional visualizations & contour plans of various tops to strata or geological thicknesses. The geological database was also used in the mid-80s for the  CIRIA Rising Water Levels in London Study and later in the 90s when assessing the site investigation needs and geology associated with Jubilee Line construction. A copy of database was eventually handed over to Imperial College Engineering Geology Department for the benefit of usage by the students.

Hydrogeologic Investigation, Framework, And Conceptual Flow Model Of The Antlers Aquifer, Southeastern Oklahoma, 1980–2022 -- https://lnkd.in/gH9QnMSy <-- shared USGS publication -- https://lnkd.in/gd8TzjJ <-- shared USGS National Water Information System (NWIS) database -- https://lnkd.in/gh9ESpFb <-- shared associated USGS open data release -- H/T Evin Fetkovich, GIT “The 1973 Oklahoma Groundwater Law (Oklahoma Statute §82–1020.5) requires that the Oklahoma Water Resources Board conduct hydrologic investigations of the State’s groundwater basins to support a determination of the maximum annual yield for each groundwater basin. Every 20 years, the Oklahoma Water Resources Board is required to update the hydrologic investigation on which the maximum annual yield determinations were based. The maximum annual yield allocated per acre of land is used to set the equal-proportionate share pumping rate. The maximum annual yield of 5,913,600 acre-feet per year and equal-proportionate-share of 2.1 acre-feet per acre per year currently (2025) in place for the Antlers aquifer were issued by the Oklahoma Water Resources Board on February 14, 1995. Because more than 20 years have elapsed since the 1995 final order for the Antlers aquifer was issued, the U.S. Geological Survey, in cooperation with the Oklahoma Water Resources Board, completed an in-depth hydrologic study that included a hydrogeologic framework and conceptual groundwater-flow model for the 1980–2022 study period. The results of an analysis of land use, long-term climate patterns, streamflow and base-flow patterns, historical groundwater use, as well as groundwater-level fluctuations across the Antlers aquifer are described. In addition, groundwater quality was analyzed for total dissolved solids concentrations and major ions for the Antlers aquifer. An updated hydrogeologic framework was developed that included refining the aquifer boundary in Oklahoma, the creation of new potentiometric surface and saturated thickness of fresh groundwater maps, one multiple-well aquifer test, slug tests, and an analysis of lithologic logs across the aquifer. A conceptual groundwater flow model and water budget were developed by incorporating estimates of recharge from precipitation, saturated-zone evapotranspiration, streambed seepage, lateral groundwater flows, vertical leakage, and withdrawals from groundwater wells…” #GIS #spatial #mapping #fedscience #water #hydrology #wateresources #pump #pumping #groundwater #AntlersAquifer #aquifer #Oklahoma #model #flow #test #flowmodel #yield #wateruse #watersecurity #climate #weather #recharge #precipitation #rainfall #TDS #waterquality #ions #potentiometric #geology #monitoring #planning #regulatory #agriculture #farming #cropland #spatialanalysis #spatiotemporal U.S. Geological Survey (USGS)

“Detecting preferential flows” Detecting preferential flow is challenging due to the inherent complexity and heterogeneity of the relevant soil structures.  Identifying voids alone is insufficient, as many do not actively transmit water during preferential flow events. Moreover, field surveys are only a snapshot of an environmental system, but flowpath arrangements can change completely within relatively short time periods depending on the level of biologic, geomorphic, and hydrologic activity.  Additionally, even when preferential flow features are successfully identified at the plot scale, these findings cannot be easily extrapolated to the whole catchment. This limitation arises because hillslopes exhibit varying hydrological responses influenced by micro-topography, soil properties, and curvature, leading to significant spatial variability in preferential flow pathways. Many different methods exist to identify and partly quantify preferential flow in soils, but each has its own limitations: “Dye tracers and sprinkling experiments” are commonly used to visualize flowpaths in soils but have the disadvantage of destroying the site during excavation for surveying. Additionally, these techniques may miss flowpaths that transport pre-event water, as these pathways will not be marked by the dye of the event water. “Soil moisture sensors” located in a depth profile can detect preferential flow, by detecting rapid increases in moisture content that exceed what would be expected from matrix flow alone. Lysimeters can be used in a similar way as the soil moisture sensors, if the outflow response occurs faster than predicted by advective or dispersive matrix transport.  Both methods, however, are limited by their spatial scale and require significant installation efforts. “Electric Resistivity Tomography (ERT) and Ground Penetrating Radar (GPR)” can be used to detect soil pipes by identifying the pipe walls and tracking them spatially through the hillslope.  The main drawback of this technique is its limited resolution, which restricts its ability to detect only larger flow features. “X-Ray and computer tomography (CT)” can be used to visualize macropore networks or other pore structures in soils.  However, as the sample volumes of the CTs are related to the resolution, the undisturbed soil cores are difficult to obtain and, due to edge effects induced by the soil coring, can alter the measured flow. “Trenched hillslopes” have also been used to detect preferential flow, particularly lateral flow. Variable wetness or observed flow volumes on the hillslope face (the excavated cross section of hillslope soil) is the result from different flowpaths.  However, trench excavation and monitoring is very labor intensive and results can only be interpreted at the plot scale. See Pyschik and Weiler (2026) in HESS, EGUsphere, “Detecting the occurrence of preferential flow in soils with stable water isotopes”

The “Geotechnical Engineering Testing Manuals” by #Hamed S. #Saeedy is a comprehensive guide for geotechnical engineers, field staff, and lab technicians. It provides a structured approach to soil testing in both laboratory and field settings. The manual is divided into two parts: Part I focuses on laboratory testing, while Part II covers #geohydrological field testing. Part I: Laboratory Testing Procedures This part outlines essential procedures to assess soil properties and classify soils for engineering purposes. 1. Introduction to Soil Testing This section explains the importance of soil testing and variability in soil behavior due to particle differences. Testing allows classification and performance evaluation to address geotechnical challenges. 2. Soil Classification Tests These tests categorize soils based on physical characteristics like moisture content, Atterberg limits, and particle size distribution. 3. Soil Strength Tests Strength tests, such as unconfined compressive strength and triaxial compression, assess soil bearing capacity and stability. 4. Soil Compressibility Tests One-dimensional consolidation tests predict soil settlement and stability under pressure. 5. Soil Permeability Tests This section describes methods, like the falling head test, to measure water flow through soil for drainage and slope stability. 6. Soil Chemical Tests Chemical tests, such as sulfate and chloride content, help evaluate how soil chemistry impacts structure durability. Part II: Geohydrological Field Manual Part II guides engineers in conducting field tests for groundwater and soil behavior, including: 1. Standard Penetration Test (SPT) SPT measures soil density and strength. 2. Sampling Techniques Methods for collecting soil samples for lab and field analysis, with instructions for proper preservation and transport. 3. Field Permeability Testing Falling and rising head tests assess water flow through soil to understand groundwater movement. 4. Pressuremeter Testing Evaluates stress-strain behavior in soil, essential for determining stiffness and strength. 5. Piezometer Installation and Groundwater Monitoring Guides the installation of piezometers to track groundwater, critical for foundation design and slope stability. Conclusion The “Geotechnical Engineering Testing Manuals” provides practical, detailed guidance on soil testing, with step-by-step procedures and calculations for accurate testing. It’s essential for geotechnical engineers, technicians, and field staff to ensure safe, reliable project outcomes. #Geotechnical #Engineering #SoilTesting #StrengthTests #Compressibility #Permeability #ChemicalTests #CivilEngineering #Construction #Drainage #FoundationDesign #Stability #WaterFlow #FieldManual #SlopeStability #BearingCapacity #Settlement #Groundwater #Sampling #HydrometerAnalysis #ShearStrength #Durability #Piezometer #Geohydrological #ASTM

GROUNDWATER EXPLORATION, RESISTIVITY SURVEY Groundwater remains one of the most critical natural resources for human survival, agriculture, and industrial development. With increasing global demand, identifying viable groundwater sources has become a priority in hydrogeological investigations. Among the various geophysical methods used for groundwater exploration, electrical resistivity survey stands out due to its reliability, cost-effectiveness, and non-invasive nature. This method plays a crucial role in mapping subsurface hydrogeological structures and detecting aquifers, especially in regions where drilling without prior knowledge can be costly or risky. ELECTRICAL RESISTIVITY METHOD The electrical resistivity method is based on the principle that different geological materials have varying abilities to resist the flow of electric current. When an electric current is introduced into the ground using electrodes, the potential differences generated are measured at the surface. By analyzing these measurements, the apparent resistivity of subsurface materials can be determined. Materials such as clay, saturated sands, and weathered zones often exhibit low resistivity values due to their high moisture content and ion mobility, whereas dry sands, rocks, and crystalline formations typically show higher resistivity. TYPES: There are various configurations and techniques used in resistivity surveys. VERTICAL ELECTRICAL SOUNDING (VES): investigates changes in resistivity with depth. It is widely used to determine aquifer depths and lithological boundaries. The Schlumberger and Wenner array configurations are popular for VES surveys. ELECTRICAL RESISTIVITY IMAGING (ERI) OR TOMOGRAPHY: This modern technique provides a two-dimensional or three-dimensional image of subsurface resistivity.

How to conduct a groundwater management study for a mining company with open pit or underground mine. This study will be carried out as follows: - 1. Carry out hydrogeological prospecting works all around the mine extension, using the electrical resistivity geophysical method. This study will serve to : - Detect the different water tables in depth, - Know the main direction of the flow of underground water from from these different water tables - Identify different successful points, where dewatering wells should be carried out. - 2. Place a series of dewatering wells at a distance of 500 to 1000 m from the mine, perpendicular to the main direction of groundwater flow. Then proceed to pump groundwater through these wells, installing o network of pipes to pump this water away from this area. So the execution of these dewatering and monitoring wells around the mine, will allow: - To identify the different lithological layers with strong water inflow - T carry out pumping test in order to know the capacity of each well and size the pumps for maximum drawdown - To determine the hydrogeological characteristics of the aquifer (K, T, Ss, Sy, ne, nt,...) - To start checking the drawdown of the water level through the monitoring wells - 3. Participate in inspection work inside the mine, for identifying differents crucks where groundwater inside the rock coming, to map them and to carry out horizontal drains for collecting these groundwater flow and direct it to the collector for installing pump station and network of pipes. - 4. Every day carried out monitoring work with the technicians, to collect technical data on the operation of pump such as the current intensity, the rotation speed of pump RPM and the pumping flow rates; and also the data on the behavior of borehole during pumping such as the water level and drawdown on each pumping and observation wells. - 5. The data collected during the monitoring work help to produce a daily, monthly, yearly report on the water balance of the mine in order to know the quantity of water pumped and see the progress of the groundwater drawdown. And finally, carry out a hydrogeological modeling with software such as Feflow, Modflow and Leapfrog hydro; to simulate groundwater flow and quantify water entering inside our domain and what hydrogeological initiatives should be planned in the future.

Hydraulic Testing in Hydrogeology Practical Guide for the Interpretation of Pumping Tests in Fractured Media   ▶️ Pumping testing is the most important terrain technique for aquifer characterization as it provides information on i) aquifer type, its hydraulic boundaries and hydraulic parameters (T, K, s), and ii) maximum extraction flow (Q) and well efficiency.   ▶️In particular, the interpretation of pumping tests in fractured media represents one of the greatest technical challenges in hydrogeology. Since, unlike porous aquifers, the underground flow in fractures is highly heterogeneous and anisotropic, so its hydraulic response rarely conforms to the assumptions of conventional analytical models. 📌In this context, a deficient interpretation of the evidence generates:  ✅Overestimation of the extraction capacity of the aquifer and/or the well,  ✅Incorrect conceptual model building and poor estimation of aquifer hydraulics parameters, ✅Poor Well Operation Plans, or Dewatering Programs, with negative operational and economic impacts. (Ref. Ferround, A., et al, 2018).   ☑️ Due to the complexity of groundwater flow in fractured rocks, it is necessary to apply interpretation criteria different from those used in porous media. This guide emphasizes the comprehensive analysis of:  ✅The Groundwater Flow Regime (radial, linear and bilinear)  +  ✅The Derived Curve  +  ✅The Recovery Curve, and  +  ✅Heterogeneity of the Environment 🔊 📢This guide proposes basic criteria to reduce uncertainty and improve the analysis and interpretation of pumping tests in Water Supply, Dewatering or Environmental Assessment projects. #PumpingTests